Telecommunications apparatus and methods

ABSTRACT

A method of operating a terminal device in a wireless telecommunications system is disclosed. The terminal device is configured to selectively switch between an active operating mode and a reduced-power operating mode. The method comprises communicating with a network entity to exchange a block of data between the terminal device and the network entity while the terminal device is in the active operating mode. The method further comprises determining when communications associated with the exchange of the block of data are complete, and in response to determining communications associated with the exchange of the block of data are complete, switching from the active operating mode to the reduced-power operating mode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.15/771,526, filed Apr. 27, 2018, which is a National Stage Applicationof PCT International Application No. PCT/EP2016/074766, filed on Oct.14, 2016, which claims priority to European Patent Application No.15193159.9, filed Nov. 5, 2015, the content of each is herebyincorporated by reference into this application.

BACKGROUND Field

The present disclosure relates to telecommunications apparatus andmethods.

Description of Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Third and fourth generation mobile telecommunication systems, such asthose based on the 3GPP defined UMTS and Long Term Evolution (LTE)architectures, are able to support more sophisticated services thansimple voice and messaging services offered by previous generations ofmobile telecommunication systems.

For example, with the improved radio interface and enhanced data ratesprovided by LTE systems, a user is able to enjoy high data rateapplications such as mobile video streaming and mobile videoconferencing that would previously only have been available via a fixedline data connection. The demand to deploy third and fourth generationnetworks is therefore strong and the coverage areas for these networksis expected to increase rapidly.

The anticipated widespread deployment of third and fourth generationnetworks has led to the parallel development of devices and applicationswhich, rather than taking advantage of the high data rates available,instead take advantage of the robust radio interface and increasingubiquity of the coverage area. Examples include so-called machine typecommunication (MTC) applications, which are typified by semi-autonomousor autonomous wireless communication devices (i.e. MTC devices)communicating small amounts of data on a relatively infrequent basis.Examples include so-called smart meters which, for example, might belocated in a customer's house and periodically transmit information backto a central MTC server relating to the customer's consumption of autility, such as gas, water, electricity and so on. Further informationon characteristics of MTC-type devices can be found, for example, in thecorresponding standards, such as ETSI TS 122 368 V12.4.0 (2014October)/3GPP TS 22.368 version 12.4.0 Release 12 [1]. Some typicalcharacteristics of MTC type terminal devices/MTC type data mightinclude, for example, characteristics such as low mobility, high delaytolerance, small data transmissions, a level of predictability fortraffic usage and timing (i.e. traffic profile), relatively infrequenttransmissions and group-based features, policing and addressing.

Unlike a conventional third or fourth generation terminal device (suchas a smartphone), an MTC-type terminal is preferably relatively simpleand inexpensive and able to operate with relatively low powerconsumption. For example, it may often be the case that an MTC-typeterminal is required to operate for an extended period of time withoutan external source of power. However, whilst it can be convenient for anMTC-type terminal to take advantage of the wide coverage area and robustcommunications interface provided by third or fourth generation mobiletelecommunication networks, there are aspects of these networks whichare not well suited to simple and inexpensive devices. This is becausesuch networks are generally optimised for use by devices that requirehigh data rates and low latency. Although power usage is an importantconsideration for such devices, it is to some extent of secondaryconcern to issues of data rates and latency. The type of functionsperformed by a typical MTC-type terminal on the other hand (for instancecollecting and reporting back data on a relatively infrequent basis) donot typically require high data rates furthermore are typically nottime-critical.

With this in mind, the inventors have recognised a desire for methodsand apparatus that allow terminal device to operate within a mobiletelecommunications network with reduced power consumption as compared toexisting approaches.

SUMMARY

The present disclosure can help address or mitigate at least some of theissues discussed above.

Respective aspects and features of the present disclosure are defined inthe appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the present technology. The described embodiments,together with further advantages, will be best understood by referenceto the following detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1 schematically represents an example of a conventional LTE-typewireless telecommunication network;

FIG. 2 schematically represents some aspects of a conventional LTE radioframe structure;

FIG. 3 schematically represents some aspects of a conventional LTEdownlink radio subframe;

FIGS. 4 to 6 schematically represent some aspects of a conventionaldiscontinuous reception (DRX) mode of a wireless telecommunicationnetwork;

FIG. 7 schematically represents some aspects of a wirelesstelecommunications network configured to operate in accordance withcertain embodiments of the present disclosure;

FIG. 8 schematically represents some aspects of a protocol stack in awireless telecommunications network configured to operate in accordancewith certain embodiments of the present disclosure; and

FIGS. 9 to 12 are ladder diagrams schematically representing someoperating aspects of a terminal device and a base station in accordancewith certain embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 provides a schematic diagram illustrating some basicfunctionality of a mobile telecommunications network/system 100operating in accordance with LTE principles and which may be adapted toimplement embodiments of the disclosure as described further below.Various elements of FIG. 1 and their respective modes of operation arewell-known and defined in the relevant standards administered by the3GPP (RTM) body, and also described in many books on the subject, forexample, Holma H. and Toskala A [2]. It will be appreciated thatoperational aspects of the telecommunications network which are notspecifically described below may be implemented in accordance with anyknown techniques, for example according to the relevant standards.

The network 100 includes a plurality of base stations 101 connected to acore network 102. Each base station provides a coverage area 103 (i.e. acell) within which data can be communicated to and from terminal devices104. Data is transmitted from base stations 101 to terminal devices 104within their respective coverage areas 103 via a radio downlink. Data istransmitted from terminal devices 104 to the base stations 101 via aradio uplink. The core network 102 routes data to and from the terminaldevices 104 via the respective base stations 101 and provides functionssuch as authentication, mobility management, charging and so on.

Terminal devices may also be referred to as mobile stations, userequipment (UE), user terminal, mobile radio, communications device, andso forth. Base stations, which are an example of network infrastructureequipment, may also be referred to as transceiverstations/nodeBs/e-nodeBs, and so forth.

Mobile telecommunications systems such as those arranged in accordancewith the 3GPP defined Long Term Evolution (LTE) architecture use anorthogonal frequency division modulation (OFDM) based interface for theradio downlink (so-called OFDMA) and a single carrier frequency divisionmultiple access scheme (SC-FDMA) on the radio uplink. FIG. 2 shows aschematic diagram illustrating an OFDM based LTE downlink radio frame201. The LTE downlink radio frame is transmitted from a LTE base station(known as an enhanced Node B) and lasts 10 ms. The downlink radio framecomprises ten subframes, each subframe lasting 1 ms. A primarysynchronisation signal (PSS) and a secondary synchronisation signal(SSS) are transmitted in the first and sixth subframes of the LTE frame.A physical broadcast channel (PBCH) is transmitted in the first subframeof the LTE frame.

FIG. 3 is a schematic diagram of a grid which illustrates the structureof an example conventional downlink LTE subframe. The subframe comprisesa predetermined number of symbols which are transmitted over a 1 msperiod. Each symbol comprises a predetermined number of orthogonalsubcarriers distributed across the bandwidth of the downlink radiocarrier.

The example subframe shown in FIG. 3 comprises 14 symbols and 1200subcarriers spread across a 20 MHz bandwidth licenced for use by theoperator of the network 100, and this example is the first subframe in aframe (hence it contains PBCH). The smallest allocation of physicalresource for transmission in LTE is a resource block comprising twelvesubcarriers transmitted over one subframe. For clarity, in FIG. 3, eachindividual resource element is not shown, instead each individual box inthe subframe grid corresponds to twelve subcarriers transmitted on onesymbol.

FIG. 3 shows in hatching resource allocations for four LTE terminals340, 341, 342, 343. For example, the resource allocation 342 for a firstLTE terminal (UE 1) extends over five blocks of twelve subcarriers (i.e.60 subcarriers), the resource allocation 343 for a second LTE terminal(UE2) extends over six blocks of twelve subcarriers (i.e. 72subcarriers), and so on.

Control channel data can be transmitted in a control region 300(indicated by dotted-shading in FIG. 3) of the subframe comprising thefirst “n” symbols of the subframe where “n” can vary between one andthree symbols for channel bandwidths of 3 MHz or greater and where “n”can vary between two and four symbols for a channel bandwidth of 1.4MHz. For the sake of providing a concrete example, the followingdescription relates to host carriers with a channel bandwidth of 3 MHzor greater so the maximum value of “n” will be 3 (as in the example ofFIG. 3). The data transmitted in the control region 300 includes datatransmitted on the physical downlink control channel (PDCCH), thephysical control format indicator channel (PCFICH) and the physical HARQindicator channel (PHICH). These channels transmit physical layercontrol information. Control channel data can also or alternatively betransmitted in a second region of the subframe comprising a number ofsubcarriers for a time substantially equivalent to the duration of thesubframe, or substantially equivalent to the duration of the subframeremaining after the “n” symbols. The data transmitted in this secondregion is transmitted on the enhanced physical downlink control channel(EPDCCH). This channel transmits physical layer control informationwhich may be in addition to that transmitted on other physical layercontrol channels.

PDCCH and EPDCCH contain control data indicating which subcarriers ofthe subframe have been allocated to specific terminals (or all terminalsor subset of terminals). This may be referred to as physical-layercontrol signalling/data. Thus, the PDCCH and/or EPDCCH data transmittedin the control region 300 of the subframe shown in FIG. 3 would indicatethat UE1 has been allocated the block of resources identified byreference numeral 342, that UE2 has been allocated the block ofresources identified by reference numeral 343, and so on.

PCFICH contains control data indicating the size of the control region(i.e. between one and three symbols for channel bandwidths of 3 MHz orgreater and between two and four symbols for channel bandwidths of 1.4MHz).

PHICH contains HARQ (Hybrid Automatic Request) data indicating whetheror not previously transmitted uplink data has been successfully receivedby the network.

Symbols in a central band 310 of the time-frequency resource grid areused for the transmission of information including the primarysynchronisation signal (PSS), the secondary synchronisation signal (SSS)and the physical broadcast channel (PBCH). This central band 310 istypically 72 subcarriers wide (corresponding to a transmission bandwidthof 1.08 MHz). The PSS and SSS are synchronisation signals that oncedetected allow a LTE terminal device to achieve frame synchronisationand determine the physical layer cell identity of the enhanced Node Btransmitting the downlink signal. The PBCH carries information about thecell, comprising a master information block (MIB) that includesparameters that LTE terminals use to properly access the cell. Datatransmitted to terminals on the physical downlink shared channel(PDSCH), which may also be referred to as a downlink data channel, canbe transmitted in other resource elements of the subframe. In generalPDSCH conveys a combination of user-plane data and non-physical layercontrol-plane data (such as Radio Resource Control (RRC) and Non AccessStratum (NAS) signalling). The user-plane data and non-physical layercontrol-plane data conveyed on PDSCH may be referred to as higher layerdata (i.e. data associated with a layer higher than the physical layer).

FIG. 3 also shows a region of PDSCH containing system information andextending over a bandwidth of R344. A conventional LTE subframe willalso include reference signals which are not shown in FIG. 3 in theinterests of clarity.

The number of subcarriers in a LTE channel can vary depending on theconfiguration of the transmission network. Typically this variation isfrom 72 sub carriers contained within a 1.4 MHz channel bandwidth to1200 subcarriers contained within a 20 MHz channel bandwidth (asschematically shown in FIG. 3). As is known in the art, data transmittedon the PDCCH, PCFICH and PHICH is typically distributed on thesubcarriers across the entire bandwidth of the subframe to provide forfrequency diversity.

A terminal device in radio resource control (RRC) connected modereceives and decodes PDCCH in subframes to identify if there are anytransmission resource allocations (resource grants) for the terminaldevice in the subframe. A terminal device is thus conventionallyrequired to receive and decode PDCCH for all subframes in which theterminal device might potentially be allocated transmission resources,even though in many of these subframes there might not be any data forthe terminal device. Resources used in receiving and decoding PDCCH insubframes for which there is no data for the terminal device are ineffect wasted. With this in mind, a known technique for lowering powerconsumption in LTE-type terminals is to restrict the number of subframesfor which a terminal device should monitor PDCCH using so-calleddiscontinuous reception, DRX, techniques. DRX techniques involve aterminal device and a base station in effect agreeing times (e.g.particular subframes) during which the terminal device will bemonitoring downlink physical channels and the base station can expectthe terminal device to receive transmissions sent to it. The terminaldevice thus knows that outside these agreed times there are subframeswhen it will not receive transmissions from the base station, and theterminal device may conserve power during these subframes by notreceiving and decoding PDCCH.

Thus, a DRX mode comprises alternating periods during which a terminaldevice could potentially receive data from the base station (and henceshould monitor PDCCH) and periods during which the terminal device willnot receive data (and hence need not monitor PDCCH to save power). Thesubframes in which the terminal device could receive data from the basestation may be referred to as DRX inactive periods and the subframes inwhich the terminal device should not receive data from the base stationmay be referred to a DRX active periods. DRX inactive periods may alsobe referred to as wake periods or non-dormant periods and DRX activeperiods may also be referred to sleep periods or dormant periods. Theprocess of transitioning from a DRX active (sleep/dormant) mode ofoperation to a DRX inactive (wake/non-dormant) mode of operation may bereferred to as waking-up. Similarly, the process of transitioning from aDRX inactive (wake/non-dormant) mode of operation to a DRX active(sleep/dormant) mode of operation may be referred to as going to sleep.Thus, a terminal device operating in a DRX inactive mode may be referredto as being awake and a terminal device operating in a DRX active modemay be referred to as being asleep.

In a conventional LTE network the timings of DRX inactive periods andDRX active periods for a given terminal device in RRC Connected mode aredefined by various parameters (which may be defined in terms of numbersof subframes). There are six basic DRX parameters that define thepattern of DRX inactive and DRX active periods in LTE (i.e. the times oftransitions between these two DRX operating modes). These are:

-   -   (i) DRX Cycle    -   (ii) On Duration Timer    -   (iii) DRX Short Cycle    -   (iv) DRX Short Cycle Timer    -   (v) DRX Inactivity Timer    -   (vi) DRX Retransmission Timer

FIGS. 4 to 7 are schematic diagrams showing how the above-identified DRXparameters are defined on a representative time axis t. (The timings inthese figures are represented for clarity of explanation and are notnecessarily shown to scale.)

FIG. 4 schematically represents the basic underlying DRX cycle withperiods when the terminal device receiver circuitry is active (awake)and monitoring PDCCH (DRX inactive mode) schematically represented bydiagonally shaded blocks on the time axis t. This aspect of the LTE DRXmode may be referred to herein as the “normal” or “basic” DRXcycle/mode. The timings relating to this normal DRX cycle are set by theparameters DRX Cycle and On Duration Timer as schematically representedin the figure. Thus, in the normal DRX mode a terminal device activatesits receiver circuitry and monitors PDCCH for a period corresponding toOn Duration Timer once every DRX Cycle.

A relatively long basic DRX cycle allows for more power to be conserved.However, a long basic DRX cycle also results in increased latencybecause there are longer periods of time during which the terminaldevice is not monitoring PDCCH (and hence cannot be contacted). Toaddress this LTE provides for two durations of DRX cycle, namely thebasic/normal DRX cycle represented in FIG. 4, and a shorter DRX cycle.The short DRX cycle is broadly similar to the normal DRX cycle inoverall structure in that it also comprises a regular pattern of DRXinactive and DRX active periods. However, the short DRX cycle adopts ashorter repeat period. The operation of the short DRX cycle is governedby the parameters DRX Short Cycle and DRX Short Cycle Timer. DRX ShortCycle is the repeat period for the short DRX cycle (DRX Cycle is aninteger multiple of DRX Short Cycle in LTE). DRX Short Cycle timerdefines the number of short DRX cycle periods before the normal DRXcycle is entered. (In LTE the On Duration Timer applies for both shortand normal DRX cycles.)

Thus a terminal device which has concluded communicating with a networkfollows the short DRX cycle mode of operation before entering thelonger/normal DRX cycle mode (assuming no communications are made duringthe period established by DRX Short cycle Timer). The principleunderlying this approach in LTE is a recognition that a terminal deviceis more likely to need to re-communicate with a network relatively soonafter a previous communication, and so a shorter DRX cycle can be usedto reduce latency for a period after a recent communication. If,however, the terminal device does not re-communicate with the basestation during this period, the terminal device may then drop into thelonger normal DRX cycle.

FIG. 5 schematically represents some aspects of the short DRX cycle inLTE. FIG. 5 is similar to, and will be understood from, FIG. 4, exceptthe left-most DRX cycle in FIG. 4 is replaced in FIG. 5 with a sectionof short DRX cycle mode. In the example of FIG. 5 the DRX Short Cycle isone-half the normal DRX Cycle. The DRX Short Cycle Timer in thisparticular timing example is taken to expire at the end of the secondDRX Short Cycle represented in FIG. 5 such that the normal (longer) DRXcycle, as represented in FIG. 4, picks up from this point.

In summary, in the absence of any transmissions to the terminal deviceor uplink scheduling requests, the DRX mode comprises a number of shortcycles followed by a longer DRX opportunity until the next DRX cyclebegins.

However, in addition to the regular and repeating DRX inactive periodsduring which a terminal device monitors PDCCH as represented in FIGS. 4and 5, LTE defines various non-repeating/irregular DRX inactive periodsduring which a terminal device is required to monitor PDCCH, and theseare schematically represented in FIG. 6.

The upper part of FIG. 6 is a timeline representing various periodsduring which a terminal device receiver is active while the lower partof FIG. 6 is a corresponding timeline representing periods during whichthe terminal device transmitter is active.

As with FIGS. 4 and 5, the upper part of FIG. 6 uses blocks to identifytimes at which the terminal device is required to monitor PDCCH.

Here it is assumed for the period of time prior to that represented inFIG. 6 the terminal device is in the normal DRX mode such as representedin FIG. 4. In the left-most DRX inactive period represented in FIG. 6(i.e. the earliest period), the terminal device receives a downlinkcommunication on PDSCH. This may be any conventional downlinkcommunication and is indicated in the figure by a solid line labelledPDSCH allocation.

In LTE, the receipt of a downlink communication initiates a timer duringwhich a terminal device is required to continue monitoring PDCCH, evenif the On Duration Timer associated with the normal regular andrepeating DRX cycle expires. This timer is set by the DRX InactivityTimer parameter. Thus, the DRX Inactivity Timer causes the DRX inactiveperiod during which the terminal device must monitor PDCCH to beextended beyond the “normal” DRX inactive period if a downlinkcommunication is received during the “normal” DRX inactive period. Thisis schematically represented by the square grid shading in FIG. 6 forthe leftmost DRX inactive period. If any further communications arereceived by the terminal device during the extended DRX inactive period,the DRX Inactivity Timer is reset, thereby extending the DRX inactiveperiod further still. Only once the DRX Inactivity Timer expires can theterminal device re-enter DRX active mode.

In response to the PDSCH allocation represented in the left-most DRXinactive period in the upper part of FIG. 6, the terminal device will,in accordance with conventional techniques, transmit uplinkacknowledgement signalling (ACK/NACK signalling) for this (schematicallyrepresented in the lower part of FIG. 6 by the chequer-board shadedblock). In LTE the terminal device sends its acknowledgement signallingfour subframes after the subframe containing the relevant PDSCHallocation. If the terminal device is unable to properly decode thePDSCH allocation it will transmit negative acknowledgement (NACK)signalling. In response to this the base station schedules aretransmission of the information comprising the PDCCH allocation. InLTE the base station has some flexibility with regards to reschedulingthe retransmission. The base station cannot reschedule the transmissionbefore a time set by HARQ RTT Timer (e.g. eight subframes) after theinitial PDSCH allocation has expired, but the base station does not needto schedule the retransmission in the subframe immediately after HARQRTT Timer expires.

Accordingly, if a terminal device cannot properly decode a PDSCHallocation and transmits corresponding negative acknowledgementsignalling, the terminal device must reactivate its receiver circuitrywhen HARQ RTT Timer expires in the expectation that the base stationwill at some stage after HARQ RTT Timer expires schedule aretransmission of the information sent in the previous PDSCH allocation.The parameter DRX Retransmission Timer specifies the amount of time theterminal device must remain active after expiry of HARQ RTT Timer tomonitor PDCCH for a resource allocation for a retransmission of theearlier PDSCH allocation that was negatively acknowledged. This periodof time during which the terminal device cannot remain in DRX activemode is schematically resented in FIG. 6 by the block with dottedshading. Although not shown in FIG. 6 for the purposes of clarity, aretransmission of a previous negatively-acknowledged PDSCH allocationmay be expected to occur during the period corresponding to the DRXRetransmission Timer, and this will require the terminal device toremain in an active mode monitoring PDCCH waiting for the retransmissionto be received on PDSCH or for the DRX Retransmission Timer to expire.

The additional periods during which the terminal device must monitorPDCCH under the DRX Inactivity Timer (grid shading in FIG. 6) and DRXRetransmission Timer (dot shading in FIG. 6) are over and above theregular short cycle and normal cycle DRX periods. The periods associatedwith the regular are repeating DRX cycles therefore remains, asindicated by the diagonal shaded blocks in FIG. 6 (with the short DRXcycle mode being triggered by the PDSCH allocation).

Thus, the left-hand half of FIG. 6 represents how the repeating andregular pattern of active and inactive DRX periods of FIGS. 4 and 5becomes disrupted when a terminal device receives downlinkcommunications and how this result in additional periods of time duringwhich the terminal device must monitor PDCCH.

The right-hand half of FIG. 6 represents another situation which resultsin a terminal device needing to monitor PDCCH outside the repeating andregular pattern of active and inactive DRX periods such as representedin FIGS. 4 and 5. This is triggered by the terminal device making ascheduling request (SR) with an uplink transmission on the physicaluplink control channel (PUCCH). A terminal device will typically do thiswhen it wishes to request uplink resources because the terminal devicehas data it needs to communicate to the network. The PDCCH SR isschematically represented in the lower part of FIG. 6 by thebrick-shaded block.

When a terminal device transmits a SR on PUCCH it can expect to receivea response from the base station on PDSCH. In order to receive theresponse, the terminal device must therefore monitor PDCCH for the PDSCHallocation message. That is to say, on sending the PUCCH SR, theterminal device must exit DRX active mode. This is schematicallyrepresented in FIG. 6 by the by the block with zigzag shading. Once theterminal device receives the PDSCH allocation in response to the PUCCHSR, the DRX Inactivity Timer is restarted as discussed above, and asschematically represented in the right-hand part of the upper timelinein FIG. 6.

Thus, the right-hand half of FIG. 6 represents how the repeating andregular pattern of active and inactive DRX periods of FIGS. 4 and 5 alsobecomes disrupted when a terminal device requests uplink resources andhow this again results in additional periods of time during which theterminal device must monitor PDCCH.

The parameters DRX Cycle, On Duration Timer, DRX Short Cycle, DRX ShortCycle Timer, DRX Inactivity Timer, and DRX Retransmission Timer whichdefine the DRX timings are shared between the base station and terminaldevice through RRC signalling in accordance with conventionaltechniques. The starting point of the DRX cycle (i.e. what might betermed its phase relative to the system frame numbering) is determinedby DRX Start Offset which is communicated through RRC signalling. Thusboth the terminal device and the network can determine from the systemframe number the particular subframes when the terminal device receivershould be active and listening to PDCCH. This allows the base station toschedule transmissions to the base station at the appropriate times andthe terminal device to activate its receiver circuitry to receive anysuch transmissions at the appropriate times.

Further information on conventional DRX operation in LTE-type networkscan be found in the relevant standards. See, for example, ETSI TS 136331 12.7.0 (2015 October)/3GPP TS 36.331 version 12.7.0 Release 12 [3],and ETSI TS 136 321 V12.7.0 (2015 October)/3GPP TS 36.321 version 12.7.0Release 12 [4].

In practice, the DRX opportunities (i.e. the times in which the terminaldevice need not monitor PDCCH—the DRX active periods) can besignificantly less than the basic DRX cycle would suggest. This isapparent from a comparison of FIG. 6 with FIG. 4, whereby FIG. 6 shows asignificant increase in the amount of time during which the terminaldevice must monitor PDCCH (i.e. the periods represented by the grid, dotand zigzag shaded blocks) over and above the times during which theterminal device must monitor PDCCH in accordance with the basic regularand repeating DRX cycles (i.e. the periods represented by the diagonalshaded blocks).

To increase the value of DRX mode operation for devices which transmitdata infrequently it has been proposed to lengthen existing DRX timingswhich are currently allowed to provide for longer sleep periods. Therehas also been proposed what may be referred to as an extended DRX modefor devices, such as MTC devices, which transmit data infrequently (e.g.as discussed in the 3GPP document R-152342, 3GPP TSG-RAN WG2 Meeting#90bis, Fukuoka, Japan, May 25-29, 2015 [5]. The extended DRX mode mayoperate on longer cycle times than the short/long cycle DRX proceduresin LTE and place the terminal device into an even lower power mode thanthe current DRX active mode (sleep mode). In this regard, the extendedDRX (eDRX) mode may be conveniently referred to as a deep sleep mode. Ithas been proposed a terminal device in an RRC connected state and whichsupports the eDRX mode may transition to eDRX active mode (deep sleep)from the DRX inactive mode (awake) in response to an explicit eDRXcommand and may transition to eDRX active mode (deep sleep) from the DRXactive mode (sleep) in response to either an explicit eDRX command orexpiry of an eDRX Timer.

In accordance with existing approaches, when a terminal device finishestransmitting data to a network it cannot enter a sleep mode (reducedpower mode) until it receives a communication from the networkinstructing the terminal device to transition to the (deep) sleep mode,for example as proposed in WO 2014/024175 [6] or until an associatedtimer expires.

Even with changes to existing DRX schemes to allow for longer and/ordeeper sleep periods, the inventors have recognised for certain types ofterminal device, such as, although not exclusively, MTC-type devices,the power costs associated with operating unnecessarily in a DRXinactive mode (i.e. awake) can represent a relatively significantincrease in their power consumption. For example, a particular exampleMTC-type device might be expected to operate with its transceivercircuitry activated for only a second or so a day. In this case, anysaving in the time during which the device remains awake (i.e. In DRXinactive mode) can represent a relatively significant saving in powerconsumption. In light of this, certain embodiments of the disclosure aredirected to increasing the time during which a terminal device mayoperate in a sleep/reduced-power mode.

FIG. 7 schematically shows a telecommunications system 500 according toan embodiment of the present disclosure. The telecommunications system500 in this example is based broadly around an LTE-type architecture. Assuch many aspects of the operation of the telecommunications system 500are known and understood and are not described here in detail in theinterest of brevity. Operational aspects of the telecommunicationssystem 500 which are not specifically described herein may beimplemented in accordance with any known techniques, for exampleaccording to the current LTE-standards.

The telecommunications system 500 comprises a core network part (evolvedpacket core) 502 coupled to a radio network part. The radio network partcomprises a base station (evolved-nodeB) 504 coupled to a plurality ofterminal devices. In this example, two terminal devices are shown,namely a first terminal device 506 and a second terminal device 508. Itwill of course be appreciated that in practice the radio network partmay comprise a plurality of base stations serving a larger number ofterminal devices across various communication cells. However, only asingle base station and two terminal devices are shown in FIG. 7 in theinterests of simplicity.

As with a conventional mobile radio network, the terminal devices 506,508 are arranged to communicate data to and from the base station(transceiver station) 504. The base station is in turn communicativelyconnected to a serving gateway, S-GW, (not shown) in the core networkpart which is arranged to perform routing and management of mobilecommunications services to the terminal devices in thetelecommunications system 500 via the base station 504. In order tomaintain mobility management and connectivity, the core network part 502also includes a mobility management entity (not shown) which manages theenhanced packet service, EPS, connections with the terminal devices 506,508 operating in the communications system based on subscriberinformation stored in a home subscriber server, HSS. Other networkcomponents in the core network (also not shown for simplicity) include apolicy charging and resource function, PCRF, and a packet data networkgateway, PDN-GW, which provides a connection from the core network part502 to an external packet data network, for example the Internet. Asnoted above, the operation of the various elements of the communicationssystem 500 shown in FIG. 7 may be broadly conventional apart from wheremodified to provide functionality in accordance with embodiments of thepresent disclosure as discussed herein.

In this example, it is assumed the first terminal device 506 is aconventional smartphone type terminal device communicating with the basestation 504 in a conventional manner. This conventional terminal device506 comprises a transceiver unit 506 a for transmission and reception ofwireless signals and a processor unit 506 b configured to control thedevice 506. The processor unit 506 b may comprise a processor unit whichis suitably configured/programmed to provide the desired functionalityusing conventional programming/configuration techniques for equipment inwireless telecommunications systems. The transceiver unit 506 a and theprocessor unit 506 b are schematically shown in FIG. 7 as separateelements. However, it will be appreciated that the functionality ofthese units can be provided in various different ways, for example usinga single suitably programmed general purpose computer, or suitablyconfigured application-specific integrated circuit(s)/circuitry. As willbe appreciated the conventional terminal device 506 will in generalcomprise various other elements associated with its operatingfunctionality.

In this example, it is assumed the second terminal device 508 is amachine-type communication (MTC) terminal device 504 adapted to supportoperation in accordance with embodiments of the present disclosure whencommunicating with the base station 504. As discussed above,machine-type communication terminal devices can in some cases betypically characterised as semi-autonomous or autonomous wirelesscommunication devices communicating small amounts of data. Examplesinclude so-called smart meters which, for example, may be located in acustomer's house and periodically transmit information back to a centralMTC server data relating to the customer's consumption of a utility suchas gas, water, electricity and so on. MTC devices may in some respectsbe seen as devices which can be supported by relatively low bandwidthcommunication channels having relatively low quality of service (QoS),for example in terms of latency. It is assumed here the MTC terminaldevice 508 in FIG. 7 is such a device.

The MTC device 508 comprises a transceiver unit 508 a for transmissionand reception of wireless signals and a processor unit 508 b configuredto control the MTC device 508. The processor unit 508 b may comprisevarious sub-units, for example a ©RX control unit, for providingfunctionality in accordance with embodiments of the present disclosureas explained further herein. These sub-units may be implemented asdiscrete hardware elements or as appropriately configured functions ofthe processor unit. Thus the processor unit 508 b may comprise aprocessor unit which is suitably configured/programmed to provide thedesired functionality described herein using conventionalprogramming/configuration techniques for equipment in wirelesstelecommunications systems. The transceiver unit 508 a and the processorunit 508 b are schematically shown in FIG. 7 as separate elements forease of representation. However, it will be appreciated that thefunctionality of these units can be provided in various different ways,for example using a single suitably programmed general purpose computer,or suitably configured application-specific integratedcircuit(s)/circuitry. It will be appreciated the MTC device 508 will ingeneral comprise various other elements associated with its operatingfunctionality.

The base station 504 comprises a transceiver unit 504 a for transmissionand reception of wireless signals and a processor unit 504 b configuredto control the base station 504 to operate in accordance withembodiments of the present disclosure as described herein. The processorunit 506 b may again comprise various sub-units, such as a schedulingunit, for providing functionality in accordance with embodiments of thepresent disclosure as explained further below. These sub-units may beimplemented as discrete hardware elements or as appropriately configuredfunctions of the processor unit. Thus, the processor unit 504 b maycomprise a processor unit which is suitably configured/programmed toprovide the desired functionality described herein using conventionalprogramming/configuration techniques for equipment in wirelesstelecommunications systems. The transceiver unit 504 a and the processorunit 504 b are schematically shown in FIG. 7 as separate elements forease of representation. However, it will be appreciated that thefunctionality of these units can be provided in various different ways,for example using a single suitably programmed general purpose computer,or suitably configured application-specific integratedcircuit(s)/circuitry. It will be appreciated the base station 504 willin general comprise various other elements associated with its operatingfunctionality.

Thus, the base station 504 is configured to communicate data with boththe conventional terminal device 506 and the terminal device 508according to an embodiment of the disclosure over respectivecommunication links 510, 512. The base station 504 is configured tocommunicate with the conventional terminal device 506 over theassociated radio communication link 510 following the establishedprinciples of LTE-based communications, and in particular usingconventional DRX procedures. However, communications between the basestation 504 and the MTC terminal device 508 operate using modified DRXprocedures in accordance with certain embodiments of the presentdisclosure as described herein. Thus, one aspect of certain embodimentsof the disclosure is that the base station is configured to operate bycommunicating with different classes of terminal device (e.g. a firstclass of terminal device, for example comprising conventional LTEterminal devices, such as smartphones, and a second class of terminaldevice, for example comprising MTC-type terminal devices) usingdifferent discontinuous reception procedures/modes. That is to say, abase station may operate to communicate with a first class (group/type)of terminal device in accordance with a first DRX mode (e.g. inaccordance with conventional DRX procedures) and to communicate with asecond class (group/type) of terminal device in accordance with a secondDRX mode (e.g. in accordance with modified procedures such as describedherein). Whether or not a particular terminal device or base stationsupports modified DRX procedures in accordance with embodiments of thepresent disclosure may be established in accordance with conventionaltechniques for sharing terminal device and base station capabilityinformation in wireless telecommunications networks, for example basedon signalling exchange during a RRC connection establishment procedure.

In this example it is assumed the base station communicates with thefirst class of terminal device, e.g. the terminal device 506, usingconventional DRX procedures, for example, following the principlesschematically represented in FIGS. 4 to 7. However, the base stationcommunicates with the second class of terminal device, e.g. the MTCterminal device 508, using modified procedures as described herein tohelp increase the amount of time the MTC terminal device can operate inthe DRX active/reduced power mode.

In broad summary, in accordance with certain embodiments of thedisclosure, a first and a second entity, for example a terminal deviceand a base station, may operate in a wireless telecommunications networkto exchange a block of data. The first entity is operable to switchbetween a first operating mode (e.g. an awake mode/a DRX inactive mode/aconnected mode) and a second operating mode (e.g. a sleep mode/a DRXactive mode/an idle mode), wherein the second operating mode is areduced-power mode as compared to the first operating mode. The firstentity is operable to exchange the block of data with the second entity(e.g. to transmit the block of data to the second entity or receive theblock of data from the second entity) while in the first operating mode,and to switch from the first operating mode to the reduced-power secondoperating mode in response to determining communications associated withthe exchange of the block of data are complete. The second entity isconfigured to assume the first entity has switched to the secondoperating mode in response to determining communications associated withthe exchange of the block of data are complete, and to take account ofthis for any further communications (for example by taking account ofwhen the first terminal device will next exit the second operating mode,for example according to a predefined timing schedule, before attemptingto contact the first entity for further communications.

FIG. 8 schematically shows some aspects of a user-plane protocol stackfor the terminal device 508 and base station 504 for the LTE-basedwireless telecommunications network 500 represented in FIG. 7. As isgenerally conventional, the protocol stack in this implementationcomprises a physical layer, PHY, a medium access control layer, MAC, aradio link control layer, RLC, and a Packet Data Convergence Protocollayer, PDCP.

The PDCP layer supports efficient transport of IP packets over the radiolink. It performs header compression, Access Stratum (AS) security(ciphering and integrity protection) and packetre-ordering/retransmission during handover.

The RLC layer on the transmitting side constructs RLC PDUs (protocoldata units) and provides the RLC PDUs to the MAC layer. The RLC layeralso performs packet re-ordering. The RLC protocol also performssegmentation/concatenation of PDCP PDUs where appropriate. On thereceiving side, the RLC protocol performs reassembly of the RLC PDUs.The RLC protocol has three operational modes, namely transparent mode(TM), acknowledged mode (AM) and unacknowledged mode (UM).

In the RLC transparent mode (TM) PDUs pass the RLC layer without anymodification and there is no RLC layer acknowledgement procedure. In theRLC unacknowledged mode (UM), service data units (SDUs) associated withhigher layers are segmented into/reassembled from PDUs and RLC headersare used, but there is again no RLC layer acknowledgement procedure. TheRLC acknowledged mode (AM) is similar to the unacknowledged mode, butalso supports RLC layer implemented automatic repeat request (ARQ)acknowledgement procedures.

RLC AM is a selective-repeat ARQ procedure, which means that only PDUswhich are missing (NACKd) are retransmitted, and unlike a stop-and-wait(SAW) procedure, the ARQ procedure allows for further transmissionswithout waiting for ACK/NACK. Further details of LTE-basedRLC-implemented acknowledgement procedures can be found, for example, inETSI TS 136 322 V12.2.0 (2015 April)/3GPP TS 36.322 version 12.2.0Release 12 [7]. One aspect of such procedures is that a poll bit is setin the header of an RLC data PDU when there is no more data fortransmission, e.g. because the transmission and retransmission buffersare empty (except for any data units currently waiting foracknowledgements) or because no further RLC data can be transmitted atthe present time, for example due to window stalling. In effect, thepoll bit in the header of an RLC data unit (PDU) indicates the data unitis the last data unit in a current group of data units comprising ablock of data being transmitted. For applications associated with thetransmission of relatively small amounts of data, the setting of a pollbit in the header of a PDU will typically indicate the associated PDU isthe final PDU of a single SDU. Thus, for each SDU (i.e. higher layermessage) a poll bit would typically be set on the final PDU, and asingle acknowledgement would be received indicating whether or not thetransmission was successful. If any PDU comprising the SDU is NACKed,then that (those) PDU (PDUs) would be retransmitted.

RLC headers for a PDU comprise a framing information field whichindicates whether or not the PDU contains the first and/or last byte ofdata from an SDU. Thus, the framing information in effect also providean indication of whether a PDU is the last PDU for a block of data.

The MAC layer lies between the RLC layer and PHY layer. It is connectedto the RLC layer through logical channels, and to the PHY layer throughtransport channels, thus the MAC protocol supports multiplexing andde-multiplexing between logical channels and transport channels. Higherlayers use different logical channels for different QoS (quality ofservice) metrics. The MAC protocol supports QoS by scheduling andprioritizing data from logical channels. The base station operates toensure radio resources are dynamically allocated to terminal devices andperforms QoS control to ensure each bearer is allocated the negotiatedQoS. The MAC layer also supports hybrid automatic repeat request (HARQ)operations.

The PHY layer provides the radio interface between communicatingentities.

Although the current example is described in the context of a generallyconventional LTE-based protocol stack, it may be expected otherimplementations may adopt modified protocol stacks. For example, whereasit might be expected that enhanced DRX (eDRX) procedures will implementa protocol stack corresponding to that which is conventionally used inLTE, in other implementations there may be, for example, fewer MAC HARQprocesses provided and existing functionality not considered necessaryfor certain implementations may be removed (for example BTYE count basedpoll trigger procedures in the RLC layer my not be considered necessaryfor some applications).

Furthermore, other implementations in accordance with embodiments of thedisclosure may be based on other wireless telecommunications systemsvariants, for example a narrowband Internet of Things “NB-IoT”implementation may be adopted in some embodiments. It may be expectedthat a NB-IoT wireless telecommunications systems may share somesimilarities with an LTE-based Telecom application systems, but mayinclude a new physical channel which might not be FDMA on uplink orwhich might, for example, use FDMA with GMSK (Gaussian minimum shiftkeying) modulation. Nonetheless, the principles described herein inrespect of the higher layers, for example RLC and MAC layers of anLTE-based implementation, may be applied in the same manner.

FIG. 9 is ladder diagram indicating signalling between the terminaldevice 508 and the base station 504 represented in FIG. 7 in accordancewith an embodiment of the disclosure. This particular implementationassumes an RLC unacknowledged mode of operation is being used totransmit data from the terminal device to the base station while theterminal device is in a DRX inactive mode (awake) in accordance withconventional techniques. It is further assumed the terminal device 508has a block of data (e.g. an SDU) which is segmented into a plurality ofPDUs. The example of FIG. 9 assumes the SDU (i.e. the block of data tobe transmitted) comprises two PDUs, namely a first PDU and a last PDU.However, it will be appreciated in other cases the block of data maycomprise only one data unit or more than two data units. In the case ofonly one data unit, that data unit may be considered the last data unit(last PDU). In the case of more than two data units, all the data unitsapart from the last data unit may in effect be handled in the same wayas the first PDU.

The RLC layer and MAC layer for each of the terminal device 508 and thebase station 504 are schematically represented in FIG. 9. The otherlayers are not shown for simplicity.

Moving from the top of the ladder diagram downwards, in a first step theUE RLC layer forwards a PDU to the UE MAC layer for transmission to thebase station. The UE MAC layer transmits this data unit to the basestation MAC layer via the physical layer (not shown in FIG. 9 forsimplicity). In this example the base station MAC layer successfullyreceives the PDU and forwards it onto the base station RLC layer andsends positive MAC layer acknowledgement signalling (ACK) back to the UEMAC layer. In the next step of the ladder diagram represented in FIG. 9,the UE RLC layer forwards the next (which in this case is the last) PDUto the UE MAC layer for transmission is to the base station. In thisexample the base station MAC layer is assumed to fail to successfullyreceive the final PDU and sends negative MAC layer HARQ acknowledgementsignalling (NACK) back to the UE MAC layer. The UE MAC layer responds byretransmitting the last PDU to the base station. In this example thebase station MAC layer successfully receives the retransmitted last PDUand forwards it onto the base station RLC layer and sends positive MAClayer acknowledgement signalling (ACK) back to the UE MAC layer. Thisconcludes the exchange of the block of data made up of the first PDU andthe last PDU from the terminal device to the base station. This processof exchanging the data may be performed in accordance with conventionaltechniques.

However, as indicated at the bottom of the ladder diagram represented inFIG. 9, in accordance with certain embodiments of the disclosure, theterminal device 508 is configured to recognise when communicationsassociated with the exchange of the block of data are complete (e.g.when it has received positive MAC layer acknowledgement signalling inrespect of the last PDU), and to switch to a reduced-power mode ofoperation (e.g. a DRX active mode) in response to this. There areseveral ways in which the terminal device can determine which is thelast PDU to be transmitted for a given block of data. For example, thismay be based on the terminal device determining that its transmissionbuffers are empty or based on framing information in an RLC header for aPDU indicating the PDU contains the last byte of an SDU. Typically thiswill be determined at the RLC layer and the RLC layer can thus indicateto the MAC layer, e.g. using the RLC header or separate signalling,which is the last PDU, so the MAC layer knows to trigger the transitionto the reduced-power mode when the MAC layer HARQ procedure indicatespositive acknowledgement signalling in respect of this PDU. In otherimplementations, the MAC layer itself may be configured to inspect theheaders of the PDUs to identify when the last PDU is transmitted.However, this may in some implementations be considered undesirablebecause it does not fully align with the usual practices associated withinter-layer operations.

In the case of switching to a DRX active mode, this procedure is drivenby the MAC layer. However, other transitions which may occur inaccordance with the other implementations, for example from a connectedmode to an idle mode, may be controlled by other layers, for example theRRC layer. In this case the completion of signalling associated with thetransfer of the block of data may be reported to the relevant layer toinitiate the transition.

FIG. 10 is similar to, and will be answered from, FIG. 9, but shows acorresponding scenario in which the MAC layer HARQ procedure in respectof the last PDU fails, for example because successful acknowledgementsignalling is not received after a threshold number of HARQretransmissions. In this case the UE MAC layer reports the MAC layerHARQ fail up to the UE RLC layer. The UE RLC layer may then initiate aretransmission (retx) of the last PDU. Thus, it is when the last PDU(re)transmission is successfully acknowledged by the MAC layer HARQprocedure that the terminal device is configured to switch to thereduced-power operating mode (i.e. DRX active in this exampleimplementation), as schematically indicated at the bottom of FIG. 10.

At the base station side, the base station knows when the base stationMAC layer transmits positive HARQ acknowledgement signalling in respectof the last PDU received from the terminal device, and so can assume theterminal device has transitioned to the reduced-power mode, and tailorits subsequent operations accordingly. For example, in the case thereduced-power mode is a DRX active mode, the base station may beconfigured to wait until the terminal device will next transition to theDRX inactive mode (i.e. wake-up) before seeking to establish contactwith the terminal device, for example to undertake furthercommunications. In this regard, once the terminal device hastransitioned to the reduced-power mode of operation in accordance withan embodiment of the disclosure, a subsequent cycle of wake and sleepperiods may be established in accordance with conventional techniques(e.g. based on conventional DRX timers as discussed above).

Although the approach represented in FIGS. 9 and 10 focuses on an RLCunacknowledged mode of operation, broadly the same principles can beapplied for an RLC transparent mode of operation. In this case the RLClayer may be configured to indicate the end of the transmission of theblock of data to the MAC layer by using of a dedicated indicator forthis purpose.

FIG. 11 is similar to, and will be understood from, FIGS. 9 and 10.However, whereas FIGS. 9 and 10 show examples for an RLC unacknowledgedmode of operation, FIG. 11 shows an example implementation in accordancewith an embodiment of disclosure using an RLC acknowledged mode (AM) ofoperation.

As indicated in the figure, in this example it is assumed an SDUcomprising a block of data to be exchanged between the terminal device508 and the base station 504 (which in this case is uplink datatransmitted from the terminal device to the base station) is segmentedinto three PDUs at the UE RLC layer. The polling bit in the header ofthe last PDU is set to indicate it is the last PDU in accordance withconventional techniques (schematically shown as an “X” in the figure).The respective PDUs are passed from the UE RLC to the UE MAC andtransmitted via the physical layer to the base station MAC layer andpassed up to the base station RLC layer in accordance with conventionaltechniques, and schematically represented in the figure by thesignalling indicated by the labels “SN=1” for the first PDU, “SN=2” forthe second PDU and “SN=3” for the third, and last, PDU. Although notshown in FIG. 11 for simplicity, it will be appreciated thetransmissions of the respective PDUs between the respective MAC layerswill be associated with MAC HARQ signalling of the kind represented inFIGS. 9 and 10 in the usual way.

On receiving the last PDU (i.e. the PDU with the poll bit set in itsheader), the base station RLC layer responds to detecting the poll bitby sending RLC layer acknowledgement signalling back to the UE RLC layer(via the other layers in the usual way). This is schematicallyrepresented in the figure by the signalling indicated by the label“ACK”.

On receiving the positive acknowledgement signalling from the basestation, the terminal device recognises that communications associatedwith the transfer of the block of data (i.e. the SDU) are complete, andthe terminal device may transition to the reduced-power mode (e.g. a DRXactive mode or an RRC idle mode depending on the specific reduced-poweroperating mode in respect of which the method is implemented).

Similarly, on transmitting the positive acknowledgement signalling fromthe base station, the base station recognises it will cause the terminaldevice to automatically switch to the reduced-power mode, and the basestation can act accordingly (i.e. treat the terminal device as havingtransitioned to the reduced power mode when determining how to undertakefurther communications with the terminal device, for example in terms ofestablishing timings for when the terminal device will be next awake andable to receive signalling). In practice, it may be appropriate for thebase station to wait for MAC layer HARQ positive acknowledgementsignalling in respect of the ACK signalling send in response todetection of the poll bit before assuming the terminal device hastransitioned to the reduced-power state.

Although the example of FIG. 11 is shown in respect of uplinksignalling, i.e. data transmission from the terminal device to the basestation, it will be appreciated the same principles apply in respect ofdownlink signalling. Here the SDU will be segmented at the base stationRLC layer and received at the terminal device RLC layer. When theterminal device receives the last PDU (i.e. a PDU containing the pollbit set in the header), the terminal device may send acknowledgementsignalling back to the base station and then transition to thereduced-power mode. The base station, on receiving the acknowledgementsignalling, may then assume the terminal device has made the transition,and again act accordingly in respect of future operations vis-à-vis theterminal device. That is to say, the terminal device may be configuredto determine when communications associated with downlink data (i.e.data transmitted from the base station to the terminal device) arecomplete, and transition to the low power mode in response to this. Thetiming of the transition to the low-power mode may be based on when theterminal device has received MAC layer HARQ positive acknowledgementsignalling in respect of an uplink status reports sent in response tothe detection of a poll bit.

Note that there is an alternative approach to that shown in FIG. 6. Inthe alternative approach, the eNB implementation is designed toexplicitly insert a MAC control element that instructs the UE to go intoDRX state. From a UE perspective, this approach is less desirable sincethe UE cannot rely on the eNB implementing this functionality. Hence theUE needs to be designed to handle the case where the eNB does notimplement this functionality (e.g. the UE battery needs to bedimensioned assuming the UE needs to apply DRX timers).

In case the base station is performing the transmission, the poll bit isset by the base station and the successful STATUS report (RLC layeracknowledgement signalling) is generated by the terminal device. Thesending of the STATUS report may, for example, be considered completeonce the MAC/L1 procedure has completed (i.e. HARQ ACK is received).

FIG. 12 is similar to, and will be generally understood from, FIG. 11,but shows a variation on that approach whereby the entity receiving theblock of data being exchanged (i.e. the base station in the example ofFIG. 12) has a mechanism for indicating to the transmitting entity (i.e.the terminal device in the example of FIG. 12) that it has its own datato transfer back to the other entity, and so the other entity shouldavoid entering the reduced power mode.

One approach by which the receiving entity can prevent the transmittingentity from entering the reduced power mode is to simply delayacknowledging the receipt of the data from the transmitting entity untilit has initiated its own transmissions back to the transmitting entity.

Thus, the upper half of FIG. 12, i.e. down as far as the transmission ofthe third (last) PDU from the UE to the base station, is the same as forFIG. 11. However, on receiving the block of data from the terminaldevice, it is assumed the higher layers at the base station generate aresponse which is to be transmitted back to the terminal device. In thisexample it is assumed the response data comprises an SDU which issegmented at the base station into two PDUs, as schematically indicatedin the figure.

Accordingly, the base station delays the sending of acknowledgementsignalling in response to the uplink PDU containing the poll bit (thissignalling is schematically indicated in FIG. 12 by the signallinglabelled “ACK SN=3”) until after it has sent the first of its twodownlink PDUs to the terminal device (represented in FIG. 12 by thearrow from the base station RLC layer to the UE RLC layer labelled“SN=1”).

On receiving the first downlink PDU from the base station, the terminaldevice recognises this PDU is received without a poll bit being set,which indicates the base station has at least one more PDU to send, andso the UE remains in the active mode, even on subsequently receiving theacknowledgement signalling (“Ack SN=3”) in response to its own previoustransmissions. When the terminal device receives the downlink PDUcontaining the polling bit (represented in FIG. 12 by the arrow from thebase station RLC layer to the UE RLC layer labelled “SN=2”), theterminal device recognises this is the last PDU of the block of downlinkdata (SDU) being transmitted by the base station, and responds withacknowledgement signalling in the usual way (this signalling isschematically indicated in FIG. 12 by the signalling labelled “ACKSN=2”).

On subsequently receiving positive MAC layer HARQ acknowledgementsignalling in respect of the report “SN=2” (not shown in FIG. 12 forsimplicity), the terminal device may transition to the reduced powermode. Similarly, on receiving the successfully report “SN=2” from theterminal device, the base station may assume the terminal device willtransition to the reduced-power mode, and configure its subsequentcommunications with the terminal device accordingly (i.e. taking accountof when the terminal device will next be awake).

As an alternative to delaying the acknowledgement signalling in respectof the initial uplink transmissions, the base station may be configuredto provide an explicit indication, for example through bespokesignalling, to indicate the terminal device should not transition to thereduced power mode.

Thus, in accordance with the principles described herein, a terminaldevice may transition to a reduced power mode more quickly than withconventional techniques, and in particular it may do this without havingto wait for any timer to expire, or having to wait for explicitsignalling from the base station to indicate it should transition to thereduced power state. The same principles can be applied regardless ofwhether the terminal device is transmitting data to the base station, orwhether the base station is transmitting data to the terminal device.

In broad summary, the terminal device is configured to determine whencommunications associated with the exchange of a block of data with thebase station are complete, and to transition into the low-power mode inresponse to this. Similarly, the base station is also configured todetermine when communications associated with the exchange of a block ofdata with the terminal device are complete, and to assume the terminaldevice will transition into the low-power mode in response to this.Thus, in accordance with some embodiments, a UE enters DRX uponcompletion of data transmission or reception without using inactivitytimer or explicit DRX command in MAC. AM RLC poll bit is set upontransmission of the last PDU in the buffer—for small data applicationsthis will often be the last PDU of a single RLC SDU. For downlink datareception, UE can enter DRX when the poll bit is received. For uplinkdata transmission, UE may be configured to enter DRX when the RLC ACK isreceived in response to setting poll bit in the last PDU transmitted inthe uplink. For UM or TM RLC the UE may be configured to automaticallyenter DRX upon transmission of last PDU in buffer.

It will be appreciated there are various modifications to the principlesdescribed above that may be adopted in other implementations. Forexample, whereas in some examples conventional poll bits and/or framinginformation is used to provide an indication a data unit is the last ofa block of data units to be exchanged for the purposes of determiningwhen to transition to a reduced-power mode, in other implementationsdifferent indications may be used, for example a new field in the RLCheader may be defined to carry an appropriate indication.

Furthermore, and as already mentioned, although the examples above haveprimarily focused on transition from a DRX inactive mode to a DRX activemode, the same principles can be adopted in respect of transitionsbetween other pairs of modes where one mode is a reduced-power mode ascompared to the other. For example, the same principles can be appliedin respect of transitions from a radio resource connected, RRC, controlmode to a radio resource control, RRC, idle mode and/or from a radioresource connected, RRC, control mode to a radio resource control, RRC,suspended mode.

In some respects, the non-reduced-power operating mode may be a mode inwhich the terminal device is configured to monitor a downlink controlchannel (e.g. PDCCH in LTE) for radio resource allocation signallingfrom the base station and the reduced-power operating mode may be a modein which the terminal device is configured to not monitor the downlinkcontrol channel for the radio resource allocation signalling from thebase station.

It will be appreciated that a base station executing methods inaccordance with embodiments of the disclosure as described herein inrespect of its communications with certain terminal devices may also becommunicating with other terminal devices in the network in accordancewith conventional techniques. For example, a base station maycommunicate with some terminal devices in accordance with embodiments ofthe disclosure described herein and other terminal devices that

It will be appreciated that while some of the above-describedembodiments have focused on examples in which a base station of thewireless telecommunications system is providing functionality inaccordance with the principles described herein, in otherimplementations similar functionality may be provided by othercomponents of the wireless telecommunications network infrastructure.For example, some, or all, of the processing described above in relationto the base station may be provided by a core network component of thewireless telecommunications system and/or similar functionality may beprovided by other infrastructure elements, such as relay nodes and/ordedicated units for supporting an ITS scheme, for example roadside units(RSUs) deployed in association with a road network to facilitatevehicle-to-vehicle communications in accordance with previously proposedschemes. In this regard a base station may be considered as one exampleof network infrastructure equipment and maybe configured to providefunctionality of the kind described herein.

Thus there has been described a method of operating a terminal device ina wireless telecommunications system, wherein the terminal device isconfigured to selectively switch between an active operating mode and areduced-power operating mode, wherein the method comprises:communicating with a network entity to exchange a block of data betweenthe terminal device and the network entity while the terminal device isin the active operating mode; determining when communications associatedwith the exchange of the block of data are complete; and in response todetermining communications associated with the exchange of the block ofdata are complete, switching from the active operating mode to thereduced-power operating mode. The terminal device supports a protocolstack comprising a physical, PHY, layer, a medium access control, MAC,layer, and a radio link control, RLC, layer, and determining whencommunications associated with the exchange of the block of data arecomplete and the device should switch to the low-power mode is performedby the radio link control, RLC, layer.

Further particular and preferred aspects of the present invention areset out in the accompanying independent and dependent claims. It will beappreciated that features of the dependent claims may be combined withfeatures of the independent claims in combinations other than thoseexplicitly set out in the claims.

Thus, the foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentinvention is intended to be illustrative, but not limiting of the scopeof the invention, as well as other claims. The disclosure, including anyreadily discernible variants of the teachings herein, define, in part,the scope of the foregoing claim terminology such that no inventivesubject matter is dedicated to the public.

Respective features of the present disclosure are defined by thefollowing numbered paragraphs:

1. A method of operating a terminal device in a wirelesstelecommunications system, wherein the terminal device is configured toselectively switch between an active operating mode and a reduced-poweroperating mode, wherein the method comprises:

-   -   communicating with a network entity to exchange a block of data        between the terminal device and the network entity while the        terminal device is in the active operating mode;    -   determining when communications associated with the exchange of        the block of data are complete; and    -   in response to determining communications associated with the        exchange of the block of data are complete, switching from the        active operating mode to the reduced-power operating mode.

2. The method of paragraph 1, wherein the terminal device supports aprotocol stack comprising a physical, PHY, layer, a medium accesscontrol, MAC, layer, and a radio link control, RLC, layer, and whereindetermining when communications associated with the exchange of theblock of data are complete is performed at the radio link control, RLC,layer.

3. The method of paragraph 1 or 2, wherein communicating with thenetwork entity to exchange the block of data comprises transmitting theblock of data from the terminal device to the network entity, whereinthe block of data is framed or segmented into one or more uplink dataunits for transmission from the terminal device to the network entity.

4. The method of paragraph 3, wherein determining when communicationsassociated with the exchange of the block of data are complete comprisesdetermining when the last one of the uplink data units comprising theblock of data has been transmitted to the network entity.

5. The method of paragraph 3 or 4, wherein determining whencommunications associated with the exchange of the block of data arecomplete comprises determining when acknowledgment signalling isreceived form the network entity which indicates the last one of theuplink data units comprising the block of data transmitted to thenetwork entity has been successfully received by the network entity.

6. The method of any of paragraphs 3 to 6, further comprising theterminal device conveying to the network entity an indicator to indicatean uplink data unit comprising the block of data is the last of theuplink data units comprising the block of data to be transmitted.

7. The method of paragraph 6, wherein the respective uplink data unitscomprising the block of data are associated with a header fortransmission, and wherein the header for the last of the uplink dataunits comprising the block of data to be transmitted comprises theindicator.

8. The method of paragraph 7, wherein the terminal device supports aprotocol stack comprising a physical, PHY, layer, a medium accesscontrol, MAC, layer, and a radio link control, RLC, layer, and whereinthe indicator is provided by the radio link control, RLC, layer settinga polling bit in the header for the last of the uplink data unitscomprising the block of data to be transmitted to a predefined value.

9. The method of paragraph 7 or 8, wherein the header for an uplink dataunit comprises a framing information field for indicating whether or notthe uplink data unit comprises the last byte of the block of data to betransmitted, and wherein the indicator is provided by the radio linkcontrol, RLC, layer setting a value for framing information field thatindicates the associated uplink data unit comprises the last byte of theblock of data to be transmitted.

10. The method of any of paragraphs 3 to 9, further comprising theterminal device receiving an indication from the network entity toindicate the terminal device should delay switching to the reduced-poweroperating mode after the communications associated with the exchange ofthe block of data are complete.

11. The method of any of paragraphs 1 to 10, wherein communicating withthe network entity to exchange the block of data comprises the terminaldevice receiving the block of data from the network entity, wherein theblock of data is segmented into one or more downlink data units fortransmission from the network entity to the terminal device.

12. The method of paragraph 11, wherein determining when communicationsassociated with the exchange of the block of data are complete comprisesdetermining when the last one of the downlink data units comprising theblock of data has been received from the network entity.

13. The method of paragraph 11 or 12, wherein determining whencommunications associated with the exchange of the block of data arecomplete comprises determining when acknowledgment signalling istransmitted by the terminal device to the network entity to indicate thelast one of the downlink data units comprising the block of datatransmitted by the network entity has been successfully received by theterminal device.

14. The method of any of paragraphs 11 to 13, further comprising theterminal device determining a downlink data unit is the last of thedownlink data units comprising the block of data to be transmitted bythe network entity by detecting an indicator transmitted by the networkentity to indicate an associated downlink data unit is the last of thedownlink data units comprising the block of data to be transmitted bythe network entity.

15. The method of paragraph 14, wherein the downlink data unitscomprising the block of data are each associated with a header fortransmission, and wherein the header for the last of the downlink dataunits comprising the block of data to be transmitted by the networkentity comprises the indicator.

16. The method of paragraph 15, wherein the terminal device supports aprotocol stack comprising a physical, PHY, layer, a medium accesscontrol, MAC, layer, and a radio link control, RLC, layer, and whereindetermining a downlink data unit is the last of the downlink data unitscomprising the block of data to be transmitted by the network entitycomprises the terminal device radio link control, RLC, layer identifyingthat a polling bit in the header for a downlink data unit is set to apredefined value.

17. The method of paragraph 15 or 16, wherein the header for a downlinkdata unit comprises a framing information field for indicating whetheror not the downlink data unit comprises the last byte of the block ofdata to be transmitted, and wherein determining a downlink data unit isthe last of the downlink data units comprising the block of data to betransmitted by the network entity comprises the terminal device radiolink control, RLC, layer identifying that a value for the framinginformation field indicates the associated downlink data unit comprisesthe last byte of the block of data to be transmitted by the networkentity.

18. The method of any of paragraphs 1 to 17, further comprising theterminal device determining it should delay switching to thereduced-power operating mode after the communications associated withthe exchange of the block of data are complete because the terminaldevice has uplink data waiting to be transmitted to the network entity.

19. The method of any of paragraphs 1 to 18,

-   -   wherein the active operating mode corresponds with a        discontinuous reception, DRX, inactive mode and the        reduced-power operating mode corresponds with a discontinuous        reception, DRX, active mode;    -   and/or;    -   wherein the active operating mode corresponds with a radio        resource connected, RRC, control mode, and the reduced-power        operating mode corresponds with a radio resource control, RRC,        idle mode;    -   and/or;    -   wherein the active operating mode corresponds with a radio        resource connected, RRC, control mode, and the reduced-power        operating mode corresponds with a radio resource control, RRC,        suspended mode.

20. The method of any of paragraphs 1 to 19, wherein the activeoperating mode is a mode in which the terminal device is configured tomonitor a downlink control channel for radio resource allocationsignalling from the network entity and the reduced-power operating modeis a mode in which the terminal device is configured to not monitor thedownlink control channel for the radio resource allocation signallingfrom the network entity.

21. The method of any of paragraphs 1 to 20, wherein the network entitycomprises a base station, a relay node, or another terminal deviceoperating in the wireless communications system.

22. A terminal device for use in a wireless telecommunications system,wherein the terminal device is configured to selectively switch betweenan active operating mode and a reduced-power operating mode, and whereinthe terminal device comprises a controller unit and a transceiver unitconfigured to operate together to:

-   -   communicate with a network entity to exchange a block of data        between the terminal device and the network entity while the        terminal device is in the active operating mode;    -   determine when communications associated with the exchange of        the block of data are complete; and    -   in response to determining communications associated with the        exchange of the block of data are complete, to switch from the        active operating mode to the reduced-power operating mode.

23. Circuitry for a terminal device for use in a wirelesstelecommunications system, wherein the terminal device is configured toselectively switch between an active operating mode and a reduced-poweroperating mode, wherein the circuitry comprises a controller element anda transceiver element configured to operate together to:

-   -   communicate with a network entity to exchange a block of data        between the terminal device and the network entity while the        terminal device is in the active operating mode;    -   determine when communications associated with the exchange of        the block of data are complete; and    -   in response to determining communications associated with the        exchange of the block of data are complete, to switch from the        active operating mode to the reduced-power operating mode.

24. A method of operating network infrastructure equipment in a wirelesstelecommunications system supporting communication between the networkinfrastructure equipment and a terminal device, wherein the terminaldevice is configured to selectively switch between an active operatingmode and a reduced-power operating mode, wherein the method comprises:

-   -   communicating with the terminal device to exchange a block of        data between the network infrastructure equipment and the        terminal device while the terminal device is in the active        operating mode;    -   determining when communications associated with the exchange of        the block of data are complete; and    -   in response to determining communications associated with the        exchange of the block of data are complete, determining that the        terminal device has switched from the active operating mode to        the reduced-power operating mode.

25. The method of paragraph 24, wherein the network infrastructureequipment supports a protocol stack comprising a physical, PHY, layer, amedium access control, MAC, layer, and a radio link control, RLC, layer,and wherein determining when communications associated with the exchangeof the block of data are complete is performed at the radio linkcontrol, RLC, layer.

26. The method of paragraph 24 or 25, wherein communicating with theterminal device to exchange the block of data comprises transmitting theblock of data from the network infrastructure equipment to the terminaldevice, wherein the block of data is framed or segmented into one ormore downlink data units for transmission from the networkinfrastructure equipment to the terminal device.

27. The method of paragraph 26, wherein determining when communicationsassociated with the exchange of the block of data are complete comprisesdetermining when the last one of the downlink data units comprising theblock of data has been transmitted to the terminal device.

28. The method of paragraph 26 or 27, wherein determining whencommunications associated with the exchange of the block of data arecomplete comprises determining when acknowledgment signalling isreceived form the terminal device which indicates the last one of thedownlink data units comprising the block of data transmitted to theterminal device has been successfully received by the terminal device.

29. The method of any of paragraphs 26 to 28, further comprising thenetwork infrastructure equipment conveying to the terminal device anindicator to indicate a downlink data unit comprising the block of datais the last of the downlink data units comprising the block of data tobe transmitted.

30. The method of paragraph 29, wherein the respective downlink dataunits comprising the block of data are associated with a header fortransmission, and wherein the header for the last of the downlink dataunits comprising the block of data to be transmitted comprises theindicator.

31. The method of paragraph 30, wherein the network infrastructureequipment supports a protocol stack comprising a physical, PHY, layer, amedium access control, MAC, layer, and a radio link control, RLC, layer,and wherein the indicator is provided by the radio link control, RLC,layer setting a polling bit in the header for the last of the downlinkdata units comprising the block of data to be transmitted to apredefined value.

32. The method of paragraph 30 or 31, wherein the header for a downlinkdata unit comprises a framing information field for indicating whetheror not the downlink data unit comprises the last byte of the block ofdata to be transmitted, and wherein the indicator is provided by theradio link control, RLC, layer setting a value for framing informationfield that indicates the associated downlink data unit comprises thelast byte of the block of data to be transmitted.

33. The method of any one of paragraphs 26 to 32, further comprising thenetwork infrastructure equipment receiving an indication from theterminal device to indicate the network infrastructure equipment shoulddelay switching to the reduced-power operating mode after thecommunications associated with the exchange of the block of data arecomplete.

34. The method of any of paragraphs 24 to 33, wherein communicating withthe terminal device to exchange the block of data comprises the networkinfrastructure equipment receiving the block of data from the terminaldevice, wherein the block of data is segmented into one or more downlinkdata units for transmission from the terminal device to the networkinfrastructure equipment.

35. The method of paragraph 34, wherein determining when communicationsassociated with the exchange of the block of data are complete comprisesdetermining when the last one of the downlink data units comprising theblock of data has been received from the terminal device.

36. The method of paragraph 34 or 35, wherein determining whencommunications associated with the exchange of the block of data arecomplete comprises determining when acknowledgment signalling istransmitted by the network infrastructure equipment to the terminaldevice to indicate the last one of the downlink data units comprisingthe block of data transmitted by the terminal device has beensuccessfully received by the network infrastructure equipment.

37. The method of any one of paragraphs 34 to 36, further comprising thenetwork infrastructure equipment determining a downlink data unit is thelast of the downlink data units comprising the block of data to betransmitted by the terminal device by detecting an indicator transmittedby the terminal device to indicate an associated downlink data unit isthe last of the downlink data units comprising the block of data to betransmitted by the terminal device.

38. The method of paragraph 37, wherein the downlink data unitscomprising the block of data are each associated with a header fortransmission, and wherein the header for the last of the downlink dataunits comprising the block of data to be transmitted by the terminaldevice comprises the indicator.

39. The method of paragraph 38, wherein the network infrastructureequipment supports a protocol stack comprising a physical, PHY, layer, amedium access control, MAC, layer, and a radio link control, RLC, layer,and wherein determining a downlink data unit is the last of the downlinkdata units comprising the block of data to be transmitted by theterminal device comprises the network infrastructure equipment radiolink control, RLC, layer identifying that a polling bit in the headerfor a downlink data unit is set to a predefined value.

40. The method of paragraph 38 or 39, wherein the header for a downlinkdata unit comprises a framing information field for indicating whetheror not the downlink data unit comprises the last byte of the block ofdata to be transmitted, and wherein determining a downlink data unit isthe last of the downlink data units comprising the block of data to betransmitted by the terminal device comprises the network infrastructureequipment radio link control, RLC, layer identifying that a value forthe framing information field indicates the associated downlink dataunit comprises the last byte of the block of data to be transmitted bythe terminal device.

41. The method of any of paragraphs 24 to 40, further comprising thenetwork infrastructure equipment determining it should delay determiningthat the terminal device has switched from the active operating mode tothe reduced-power operating mode because the network infrastructureequipment has uplink data waiting to be transmitted to the terminaldevice.

42. The method of any of paragraphs 24 to 41,

-   -   wherein the active operating mode corresponds with a        discontinuous reception, DRX, inactive mode and the        reduced-power operating mode corresponds with a discontinuous        reception, DRX, active mode;    -   and/or;    -   wherein the active operating mode corresponds with a radio        resource connected, RRC, control mode, and the reduced-power        operating mode corresponds with a radio resource control, RRC,        idle mode;    -   and/or;    -   wherein the active operating mode corresponds with a radio        resource connected, RRC, control mode, and the reduced-power        operating mode corresponds with a radio resource control, RRC,        suspended mode.

43. The method of any of paragraphs 24 to 42, wherein the activeoperating mode is a mode in which the network infrastructure equipmentis configured to transmit radio resource allocation signalling to theterminal device on a downlink control channel and the reduced-poweroperating mode is a mode in which the network infrastructure equipmentis configured to not transmit radio resource allocation signalling tothe terminal device on thr downlink control channel.

44. The method of paragraph 24 wherein the terminal device comprises abase station, a relay node, or another network infrastructure equipmentoperating in the wireless communications system.

45. Network infrastructure equipment for use in a wirelesstelecommunications system supporting communication between the networkinfrastructure equipment and a terminal device, wherein the terminaldevice is configured to selectively switch between an active operatingmode and a reduced-power operating mode, and wherein the networkinfrastructure equipment comprises a controller unit and a transceiverunit configured to operate together to:

-   -   communicate with the terminal device to exchange a block of data        between the network infrastructure equipment and the terminal        device while the terminal device is in the active operating        mode;    -   determine when communications associated with the exchange of        the block of data are complete; and    -   in response to determining communications associated with the        exchange of the block of data are complete, to determine that        the terminal device has switched from the active operating mode        to the reduced-power operating mode.

46. Circuitry for network infrastructure equipment for use in a wirelesstelecommunications system supporting communication between the networkinfrastructure equipment and a terminal device, wherein the terminaldevice is configured to selectively switch between an active operatingmode and a reduced-power operating mode, wherein the circuitry comprisesa controller element and a transceiver element configured to operatetogether to:

-   -   communicate with the terminal device to exchange a block of data        between the network infrastructure equipment and the terminal        device while the terminal device is in the active operating        mode;    -   determine when communications associated with the exchange of        the block of data are complete; and    -   in response to determining communications associated with the        exchange of the block of data are complete, to determine that        the terminal device has switched from the active operating mode        to the reduced-power operating mode.

REFERENCES

[1] ETSI TS 122 368 V12.4.0 (2014 October)/3GPP TS 22.368 version 12.4.0Release 12

[2] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based radioaccess”, John Wiley and Sons, 2009

[3] ETSI TS 136 331 V12.7.0 (2015 October)/3GPP TS 36.331 version 12.7.0Release 12

[4] ETSI TS 136 321 V12.7.0 (2015 October)/3GPP TS 36.321 version 12.7.0Release 12

[5] R-152342, 3GPP TSG-RAN WG2 Meeting #90bis, Fukuoka, Japan, May25-29, 2015

[6] WO 2014/024175

[7] ETSI TS 136 322 V12.2.0 (2015 April)/3GPP TS 36.322 version 12.2.0Release 12

What is claimed is:
 1. A method of operating a terminal device in awireless telecommunications system, wherein the terminal device isconfigured to selectively switch between an active operating mode and areduced-power operating mode, the method comprising: communicating witha network entity to exchange a block of data between the terminal deviceand the network entity while the terminal device is in the activeoperating mode; determining when communications associated with theexchange of the block of data are complete; and in response todetermining communications associated with the exchange of the block ofdata are complete, switching from the active operating mode to thereduced-power operating mode.
 2. The method of claim 1, wherein theterminal device supports a protocol stack comprising a physical, PHY,layer, a medium access control, MAC, layer, and a radio link control,RLC, layer, and wherein determining when communications associated withthe exchange of the block of data are complete is performed at the radiolink control, RLC, layer.
 3. The method of claim 1, whereincommunicating with the network entity to exchange the block of datacomprises transmitting the block of data from the terminal device to thenetwork entity, wherein the block of data is framed or segmented intoone or more uplink data units for transmission from the terminal deviceto the network entity.
 4. The method of claim 3, wherein determiningwhen communications associated with the exchange of the block of dataare complete comprises determining when the last one of the uplink dataunits comprising the block of data has been transmitted to the networkentity.
 5. The method of claim 3, wherein determining whencommunications associated with the exchange of the block of data arecomplete comprises determining when acknowledgment signaling is receivedform the network entity which indicates the last one of the uplink dataunits comprising the block of data transmitted to the network entity hasbeen successfully received by the network entity.
 6. The method of claim3, further comprising the terminal device conveying to the networkentity an indicator to indicate an uplink data unit comprising the blockof data is the last of the uplink data units comprising the block ofdata to be transmitted.
 7. The method of claim 6, wherein the respectiveuplink data units comprising the block of data are associated with aheader for transmission, and wherein the header for the last of theuplink data units comprising the block of data to be transmittedcomprises the indicator.
 8. The method of claim 7, wherein the terminaldevice supports a protocol stack comprising a physical, PHY, layer, amedium access control, MAC, layer, and a radio link control, RLC, layer,and wherein the indicator is provided by the radio link control, RLC,layer setting a polling bit in the header for the last of the uplinkdata units comprising the block of data to be transmitted to apredefined value.
 9. The method of claim 7, wherein the header for anuplink data unit comprises a framing information field for indicatingwhether or not the uplink data unit comprises the last byte of the blockof data to be transmitted, and wherein the indicator is provided by theradio link control, RLC, layer setting a value for framing informationfield that indicates the associated uplink data unit comprises the lastbyte of the block of data to be transmitted.
 10. The method of claim 3,further comprising the terminal device receiving an indication from thenetwork entity to indicate the terminal device should delay switching tothe reduced-power operating mode after the communications associatedwith the exchange of the block of data are complete.
 11. The method ofclaim 1, wherein communicating with the network entity to exchange theblock of data comprises the terminal device receiving the block of datafrom the network entity, wherein the block of data is segmented into oneor more downlink data units for transmission from the network entity tothe terminal device.
 12. The method of claim 11, wherein determiningwhen communications associated with the exchange of the block of dataare complete comprises determining when the last one of the downlinkdata units comprising the block of data has been received from thenetwork entity.
 13. The method of claim 11, wherein determining whencommunications associated with the exchange of the block of data arecomplete comprises determining when acknowledgment signaling istransmitted by the terminal device to the network entity to indicate thelast one of the downlink data units comprising the block of datatransmitted by the network entity has been successfully received by theterminal device.
 14. The method of claim 11, further comprising theterminal device determining a downlink data unit is the last of thedownlink data units comprising the block of data to be transmitted bythe network entity by detecting an indicator transmitted by the networkentity to indicate an associated downlink data unit is the last of thedownlink data units comprising the block of data to be transmitted bythe network entity.
 15. The method of claim 14, wherein the downlinkdata units comprising the block of data are each associated with aheader for transmission, and wherein the header for the last of thedownlink data units comprising the block of data to be transmitted bythe network entity comprises the indicator.
 16. The method of claim 15,wherein the terminal device supports a protocol stack comprising aphysical, PHY, layer, a medium access control, MAC, layer, and a radiolink control, RLC, layer, and wherein determining a downlink data unitis the last of the downlink data units comprising the block of data tobe transmitted by the network entity comprises the terminal device radiolink control, RLC, layer identifying that a polling bit in the headerfor a downlink data unit is set to a predefined value.
 17. The method ofclaim 15, wherein the header for a downlink data unit comprises aframing information field for indicating whether or not the downlinkdata unit comprises the last byte of the block of data to betransmitted, and wherein determining a downlink data unit is the last ofthe downlink data units comprising the block of data to be transmittedby the network entity comprises the terminal device radio link control,RLC, layer identifying that a value for the framing information fieldindicates the associated downlink data unit comprises the last byte ofthe block of data to be transmitted by the network entity.
 18. Themethod of claim 1, wherein the active operating mode is a mode in whichthe terminal device is configured to monitor a downlink control channelfor radio resource allocation signaling from the network entity and thereduced-power operating mode is a mode in which the terminal device isconfigured to not monitor the downlink control channel for the radioresource allocation signaling from the network entity.
 19. A terminaldevice for use in a wireless telecommunications system, wherein theterminal device is configured to selectively switch between an activeoperating mode and a reduced-power operating mode, the terminal devicecomprising: a controller unit and a transceiver unit configured tooperate together to: communicate with a network entity to exchange ablock of data between the terminal device and the network entity whilethe terminal device is in the active operating mode; determine whencommunications associated with the exchange of the block of data arecomplete; and in response to determining communications associated withthe exchange of the block of data are complete, to switch from theactive operating mode to the reduced-power operating mode.
 20. Circuitryfor a terminal device for use in a wireless telecommunications system,wherein the terminal device is configured to selectively switch betweenan active operating mode and a reduced-power operating mode, thecircuitry comprising: a controller element and a transceiver elementconfigured to operate together to: communicate with a network entity toexchange a block of data between the terminal device and the networkentity while the terminal device is in the active operating mode;determine when communications associated with the exchange of the blockof data are complete; and in response to determining communicationsassociated with the exchange of the block of data are complete, toswitch from the active operating mode to the reduced-power operatingmode.